Odontidium himalongissimum Jüttner, D.M.Williams & E.J.Cox, 2017

Jüttner, I., Williams, D. M., Gurung, S., Vijver, B. Van De, Levkov, Z., Sharma, C. M., Sharma, S. & Cox, E. J., 2017, The genus Odontidium (Bacillariophyta) in the Himalaya-a preliminary account of some taxa and their distribution, Phytotaxa 332 (1), pp. 1-21 : 7-9

Odontidium himalongissimum Jüttner, D.M.Williams & E.J.Cox , sp. nov. ( Figs 23–39 )

LM ( Figs 23–31 ): Valves linear to linear-elliptic with slightly protracted, rounded apices ( Figs 23 – 31 ). Valve margins of larger cells more or less parallel, tapering close to poles. Valve dimensions (n=30): length 10.0 – 56.5 μm, width 5.5 – 8.5 μm. Transapical ribs primary, secondary ribs rarely present. Transapical ribs perpendicular or at an angle to sternum, (2) 3 – 5 in 10 μm. Striae between ribs parallel or at an angle to sternum, becoming slightly radiate towards apices, 2 – 6(9) rows between ribs. SEM ( Figs 32–39 ): external valve surface smooth or slightly rippled. Larger and smaller spines occasionally present in 2 – 3 rows along valve margin and valve face near mantle. Single row of spines sometimes extending around apices ( Figs 33 – 35, 38, 39 ). Number of spines variable, spines absent in some valves ( Fig. 32 ). Spines positioned on virgae. Virgae of similar width, vimines much shorter. Striae uniseriate, parallel and slightly radiate towards apices. Sternum ill-defined, wide, narrowing close to and extending into apical pore fields ( Figs 32 – 35 ). One rimoportula per valve present near apical pore field, replacing 3–5 vimines within a stria. External rimoportula opens as a simple slit. Internally, rimoportula possesses two protruding lips ( Figs 32, 33, 35, 37 ). Apical pore field at each apex composed of round porelli ( Figs 35, 37 ). Internally ribs perpendicular or at an angle to valve margin ( Figs 36, 37 ).

Type: — INDIA, tributary to the Sundardhunga Gâd, Kumaon, Phil Brewin , 19.10.1995. The holotype is slide no. NMW.C.2007.006.P57, National Museum Wales, Cardiff, UK!.

Etymology: —The name refers to the Himalayan Mountains where the new species is found.

Ecology and distribution:— Odontidium himalongissimum was found on stones in streams of the Pindari River catchment, Kumaon Himalaya, north-west India (NMW.C.2007.006.P52, P53, P57, P67), in the Julma and Mugu districts (NMW.C.2007.006.D23, S36) and in the Manaslu region of western Nepal (NMW.C.2007.006.MS43, MS58). The alpine streams were located between 2800 and 3750 m a.s.l. and the stream bed substratum was either dominated by cobbles and boulders, or by pebbles, rarely by gravel. Conductivity varied between 18 and 260 μs/cm, but was 150 μs/cm or less in most streams ( Table 2).

Figures

FIGURES 23–31. Odontidium himalongissimum. LM. Valve views. NMW.C.2007.006.P57: tributary to the Sundardhunga Gâd, Kumaon, India. Scale bar = 10 μm.

FIGURES 32–39. Odontidium himalongissimum. SEM. Figs 32–34. Valve views. Fig. 35. Apical pore field and rimoportula. Figs 36–37. Internal view of valves. Figs 38–39. Frustules in girdle view. NMW.C.2007.006.P67: tributary to the Pindar River, Kumaon, India. Scale bars = 5 μm (Figs 32–34), 4 μm (Figs 36, 38, 39), 2 μm (Figs 35, 37).